Immediate vs. Delayed Insertion of Copper T 380A IUD After Termination of Pregnancy Over 12-weeks Gestation: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Immediate vs. Delayed Insertion of Copper T 380A IUD After Termination of Pregnancy Over 12-weeks Gestation (NCT00540046), a randomized na study. The primary outcome is Use of IUD.

2. Clinical Question

3. Trial Design

This was a randomized, parallel-group trial comparing two timings for insertion of the same device after termination of pregnancy over 12 weeks of gestation. The registry lists allocation as randomized and masking as none. The two arms were named A/Immediate and B/Delayed. Immediate insertion was specified as within 15 minutes after delivery of the placenta immediately following the procedure; delayed insertion was specified for the post-operative visit within 2-4 weeks following the procedure.

The registry lists enrollment as 215 and the study status as completed. The recorded study start is 2007-04 and primary completion is 2010-02. The phase is listed as NA. NYU Langone Health is identified as the sponsor. These registry entries describe the study record, but do not establish how closely every participant followed the assigned timing or what procedures were used to manage deviations.

The primary outcome record gives 58 participants using an IUD in the immediate arm, with an arm count of 71, and 25 in the delayed arm, with an arm count of 88. These are the counts attached to the posted primary outcome. The registry record does not explain how these outcome counts relate to the enrollment figure, or provide a participant flow account with reasons for any differences. It also does not report the trial's original sample-size justification or a detailed statistical analysis plan. Randomization supports a design intended to compare assigned groups, while the lack of masking and missing operational details limit what can be established about conduct from the record alone.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

Reasons for not completing this period:

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

Population: 215 subjects were enrolled and randomized to the A/Immediate or B/Delayed group.

6. Primary Endpoint

The registry lists the primary outcome as Use of IUD, measured over 6 months.

The primary endpoint is the number of participants using a Copper T 380A IUD 6 months after surgery. In the registry record, it is a participant count, rather than a continuous measurement such as a score or a time duration. The posted counts are 58 in the immediate arm and 25 in the delayed arm, alongside respective outcome arm counts of 71 and 88.

Use at follow-up addresses whether participants were recorded as using the device at the specified assessment time. This endpoint is relevant to a comparison of insertion timing because both arms involve the same IUD, while the timing strategy differs. The endpoint does not, by itself, describe all aspects of device use, the duration of use between surgery and follow-up, or why a participant was not counted as using an IUD. Those details are not reported in the registry record.

The outcome is also distinct from expulsion, which is listed as a secondary outcome. A participant's recorded use at 6 months should not be treated as a direct measure of expulsion unless the record defines it that way; no such definition is reported. Nor does the endpoint alone capture other clinical outcomes or patient experiences. Its interpretation is therefore specific: it summarizes the posted count using an IUD at the stated follow-up, without establishing the pathway leading to that status.

7. Results Posted in the Registry

• B/Delayed: 28.4% (25/88) versus 81.7% (58/71) on control; risk difference -53.3 percentage points (95% CI -66.3 to -40.3), risk ratio 0.35 (0.25–0.49); unadjusted two-proportion z-test p = <0.001.

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is binary at the participant level: a participant was counted as using an IUD at 6 months or was not counted in that category. The registry reports the number meeting the outcome in each arm and the corresponding arm counts. General statistical explanation: a binary outcome can be summarized as a proportion within each group, then compared between groups. The proportion is useful because it expresses the outcome count relative to the group size, while the count alone is influenced by the size of the group. The posted comparison uses the risk difference, with delayed insertion contrasted against immediate insertion.

What does the risk difference describe?

General statistical explanation: a risk difference is the proportion with the outcome in one group minus the proportion in the other group. It is expressed on the same scale as the proportions, and a value below zero under a delayed-minus-immediate contrast indicates a lower observed outcome proportion in the delayed group. The registry reports a risk difference of -0.533, with a confidence interval from -0.663 to -0.403. Those values are reported estimates; no new calculation is needed to interpret their direction. The risk difference is an absolute contrast, which makes it distinct from relative measures.

Why are relative measures also reported?

General statistical explanation: a relative risk compares the outcome proportions between groups, while an odds ratio compares the odds of the outcome. Relative measures can describe the strength of a contrast in relation to the reference group, but may appear numerically different from an absolute difference because they use different scales. Here, the registry reports a relative risk of 0.348, with a confidence interval from 0.245 to 0.493, and an odds ratio of 0.089, with a confidence interval from 0.042 to 0.19. All three measures refer to the same binary primary outcome and the delayed-versus-immediate comparison; they should not be treated as separate findings.

How should the p-value be read?

The reported p-value is p < 0.001. General statistical explanation: a p-value assesses how compatible the observed data are with a specified null hypothesis, assuming the statistical model and other assumptions used for the test. It is not the probability that the null hypothesis is true, and it does not measure the size of an effect or its practical importance. The registry record does not report whether the test was adjusted for other variables or how any analysis assumptions were checked. The p-value should therefore be read alongside the effect estimates and their confidence intervals, not as a stand-alone summary.

What does randomization contribute?

General statistical explanation: random allocation is intended to make the assigned groups comparable on average with respect to factors that might affect the outcome. This can support a causal interpretation of an assigned-treatment contrast when the trial's conduct and analysis preserve the benefits of randomization. The registry identifies the study as randomized and parallel, but does not report the sequence-generation method, allocation concealment, handling of departures from assigned timing, or analysis population. Masking is listed as none. The record therefore supports describing the design as randomized and unmasked, but not asserting specific safeguards or procedures that are not documented.

What is not documented about the analysis?

The record lists no posted analyses, and it does not provide a detailed statistical analysis plan. The original sample-size assumptions are not reported. Missing-data handling, covariate adjustment, the definition of the analysis population, and any method for accounting for multiple outcomes are also not reported in the registry record. General statistical explanation: these choices matter because they affect which participants contribute to an estimate, how uncertainty is quantified, and how results are interpreted when several outcomes are examined. Their absence from the record does not show that no procedures existed; it means they cannot be characterized from the registry information.

The secondary outcome list includes expulsion, but no estimate for that outcome is posted. The primary comparison can therefore be interpreted as a reported unadjusted contrast in the 6-month use outcome, with its estimate, confidence interval, and p-value. It cannot answer questions about unreported endpoints, subgroup effects, or robustness to alternative analyses. General statistical explanation: a complete interpretation of a trial combines the outcome definition, group counts, effect estimate, uncertainty, and analysis methods. Where the registry does not document part of that chain, conclusions should remain limited to the statistics and design details it does report.

10. Confidence Intervals and Precision

The confidence interval for the risk difference runs from -0.663 to -0.403. It gives a range of values compatible with the observed data under the method used to construct the interval and its assumptions. Because the full analysis method is not reported in the registry record, that method cannot be described in more detail. The interval lies on the negative side of zero for the delayed-minus-immediate contrast, which is consistent with a lower recorded outcome proportion in the delayed arm.

General statistical explanation: an interval's width conveys statistical precision. A narrower interval indicates less uncertainty about the estimate under the model; a wider interval indicates more. An interval does not mean that the true effect has a specified probability of falling within its endpoints after the data are observed. It also does not account for every possible source of uncertainty, such as misclassification, missing outcomes, or differences between the registry's analysis and the trial's conduct.

The relative risk interval, from 0.245 to 0.493, and the odds ratio interval, from 0.042 to 0.19, provide uncertainty ranges on their respective relative scales. They should not be compared directly with the risk-difference interval as if all three used the same units. The registry also reports p < 0.001, but that threshold does not replace the interval as a description of the range of effect estimates compatible with the data.

The record does not report a prespecified clinically important difference or a target precision. Statistical precision can therefore be described from the posted intervals, but not judged against a stated clinical threshold in the registry.

11. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The sample-size planning figures are participants per arm, not total events. They are planning illustrations based on the observed effect, rather than the trial's own original design assumptions; those original assumptions are not reported in the registry record. The stated planning setup uses a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. For each effect scenario, the target is the stated fraction of the observed effect.

The 80% power column means the number of participants per arm used in the planning calculation to give an 80% chance of detecting the assumed effect under that setup, if the assumptions hold. The 90% power column gives the corresponding per-arm planning requirement for a 90% chance. These percentages refer to the probability of detecting the specified effect under the planning model, not the probability that the effect is real. The displayed scenarios consider planning for the full observed effect, 75% of the observed effect, and 50% of the observed effect. The smaller assumed effects require more participants per arm than the larger assumed effects.

These figures are not observed power and do not describe the power achieved by the completed trial. They are illustrative planning values derived from the posted effect and the stated assumptions. The record does not report whether the original trial design used these assumptions, or whether its original sample-size calculation used a different target, method, or effect size. A planning curve should be read as expressing the same relationship: when a study is designed to detect a smaller effect while keeping the other planning assumptions fixed, the participant requirement rises.

12. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, p₀ and p₁ are the control and treatment proportions, and p̄ is their average.

Worked calculation for this trial

1. Control proportion p₀ = 0.817; treatment proportion p₁ = 0.284; average p̄ = 0.550.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.7035 = 1.3788.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.5941 = 0.5000.
4. n = (1.3788 + 0.5000)² / (-0.5328)² = 12.4, rounded up to 13 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
p0 <- 0.816901408450704                          # control proportion
p1 <- 0.284090909090909                          # treatment proportion
n_per_arm <- function(power, frac = 1) {
  q1 <- p0 + (p1 - p0) * frac               # smaller effect = fraction of the observed difference
  pbar <- (p0 + q1) / 2
  z_b <- qnorm(power)
  ceiling(round((z_a * sqrt(2 * pbar * (1 - pbar)) + z_b * sqrt(p0 * (1 - p0) + q1 * (1 - q1)))^2 / (q1 - p0)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (unrounded n per arm)
cat("power.prop.test:", round(power.prop.test(p1 = p0, p2 = p1, power = 0.80)$n, 1), "\n")

# Simulation: how often does the z-test reject at the 80%-power sample size?
set.seed(540046)
n    <- n_per_arm(0.80)
reps <- 20000
x0 <- rbinom(reps, n, p0); x1 <- rbinom(reps, n, p1)
ph <- (x0 + x1) / (2 * n)
z  <- ((x1 - x0) / n) / sqrt(ph * (1 - ph) * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE), reps))

Output from running the code

100% of observed effect: n per arm = 13 (80% power), 17 (90% power)
 75% of observed effect: n per arm = 23 (80% power), 29 (90% power)
 50% of observed effect: n per arm = 47 (80% power), 62 (90% power)
power.prop.test: 12.4 
Simulated power at n = 13 per arm: 0.873 (20000 replicates)

The simulation draws many pairs of event counts at the planned sample size and counts how often the two-proportion z-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

13. Multiplicity, Missing Data and Analysis Populations

The registry identifies the primary outcome as IUD use at 6 months and lists expulsion as a secondary outcome. It records two outcome measures and one posted secondary outcome, but no outcome estimate for expulsion is available in the record. The registry lists no posted analyses. It does not report whether the trial tested multiple outcomes, whether any multiplicity adjustment was planned, or how the primary outcome was designated in the analysis plan. These details are not reported in the registry record.

General statistical explanation: when several outcomes or comparisons are tested, the chance of obtaining at least one apparently unusual result can increase if each test is treated independently at the same threshold. Methods to address multiplicity may adjust interpretation or testing, but the appropriate approach depends on the prespecified questions and analysis plan. Because that plan is not reported, it is not possible to determine whether the posted p-value accounts for any other analyses. The p-value should be understood as the reported value for the displayed primary comparison, not as evidence about how all possible tests were handled.

The record does not describe missing-data methods, reasons for missing outcome measurements, or whether all randomized participants were included in the primary analysis. The outcome counts are 71 in the immediate arm and 88 in the delayed arm, while the record lists enrollment as 215; it provides no participant flow explanation reconciling these figures. This should not be interpreted as a particular amount or reason for missingness. The record also does not state whether the analysis followed an intention-to-treat, per-protocol, or other population definition.

General statistical explanation: missing outcomes can affect estimates when the likelihood of being observed is related to group assignment or the outcome itself. Analysis-population definitions also matter because they determine which participants contribute to a comparison. Without the registry's missing-data procedures and analysis-population rules, the extent and direction of any resulting impact cannot be assessed. The absence of these details limits evaluation of the robustness of the reported estimate, but does not establish that a specific bias occurred.

14. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent non-serious adverse event terms

The registry lists serious adverse event figures for an at-risk count of 104 in the immediate group and 111 in the delayed group. The serious adverse event count is 0 in each group. The record gives other adverse event counts of 2 for the immediate group and 0 for the delayed group, with the same respective at-risk counts listed for those figures. Death counts are not reported in the registry record.

These figures should be read as the registry's posted counts, not as a complete account of all safety outcomes. The safety denominators differ from the arm counts attached to the primary outcome, and the record does not explain the distinction or provide participant-level follow-up information. It also does not give event descriptions for the two other adverse events or specify whether events were assessed as related to the device or procedure. The serious adverse event terms list is empty.

General statistical explanation: a count of zero means no event was recorded in that category in the listed group and period; it does not establish that the underlying risk is zero. Interpretation depends on the definition of an event, duration and completeness of surveillance, and how events were collected. Those details are not reported in the registry record, so safety comparisons should remain limited to the posted counts.

15. What the Result Does, and Does Not, Mean

The result describes an observed difference between randomized arms in the number of participants recorded as using a Copper T 380A IUD 6 months after surgery. The registry reports 58 participants using an IUD in the immediate arm and 25 in the delayed arm, with outcome arm counts of 71 and 88, respectively. The estimated risk difference for delayed versus immediate insertion is -0.533, with a confidence interval from -0.663 to -0.403, and the reported p-value is p < 0.001.

This finding is specific to the posted primary endpoint, the study population recorded in the registry, and the comparison of insertion timing after termination of pregnancy over 12 weeks of gestation. It does not describe every possible benefit or harm of either timing strategy. It does not provide a result for expulsion, despite that outcome being listed as secondary, and it does not explain the mechanisms behind the recorded difference. The outcome count alone cannot show whether a participant did not receive an insertion, experienced expulsion, stopped use, or had another reason for not being counted as using an IUD at follow-up.

The registry identifies a randomized design, which is relevant when interpreting a group comparison, but it does not provide enough information to assess all trial procedures or analytic choices. In particular, detailed outcome ascertainment, missing-data handling, analysis-population definitions, and the statistical plan are not reported. The posted contrast should therefore be described as the reported comparison rather than extended to unreported outcomes or subgroups.

General statistical explanation: a statistically small p-value does not determine whether an effect is clinically important, and a confidence interval does not resolve limitations in measurement or follow-up. The record does not state a threshold for clinical importance. The result can be described in terms of direction, magnitude, and statistical uncertainty, while the practical meaning and broader applicability remain dependent on information not contained in the registry record.

16. Why This Trial Matters Statistically

This trial illustrates a statistical comparison in which the device is the same across arms and the assigned strategy differs by timing. That structure makes the primary contrast easy to state: use at 6 months after immediate insertion versus use after insertion planned for the post-operative visit. The endpoint is binary, so the posted counts can be summarized with an absolute risk difference and relative measures such as a risk ratio and odds ratio.

The result also shows why effect measures should be interpreted on their own scales. The risk difference communicates the absolute contrast in outcome proportions, while the relative risk and odds ratio express comparisons relative to the other group. Reporting more than one scale can aid interpretation, but the estimates do not represent independent evidence because they summarize the same primary outcome and groups. Their confidence intervals offer information about statistical precision that the p-value alone does not convey.

Randomization is a central feature of the design, but statistical interpretation also depends on information about trial conduct and analysis. The registry does not report detailed handling of missing data, analysis populations, multiplicity, or the original sample-size assumptions. The primary outcome group counts and the enrollment figure are not reconciled in a participant-flow account. These gaps make clear that a reported estimate, even with a small p-value, is only one part of evaluating a trial.

The record is also a useful example of the boundary between a posted result and broader claims. The primary endpoint concerns IUD use at a specified follow-up, while expulsion is only listed as a secondary outcome without a posted result. Keeping interpretation tied to the measured endpoint avoids treating an outcome count as an explanation of the events that led to it.

17. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

Several trial-specific details needed to evaluate the posted comparison are not reported in the registry record. The record does not provide a participant-flow account explaining how the enrollment figure relates to the arm counts used for the primary outcome, nor does it state why any participants may not appear in those outcome counts. This prevents a clear assessment of outcome completeness from the registry information alone.

The endpoint is described as the number of participants using a Copper T 380A IUD 6 months after surgery, but the record does not give a detailed operational definition of use or explain how it was ascertained. The listed secondary outcome, expulsion, has no posted result. The record does not describe the duration or method of safety surveillance, event attribution, or the nature of the other adverse events counted in the immediate arm.

Although allocation is identified as randomized, the sequence-generation and allocation-concealment methods are not reported. Masking is listed as none. The record does not explain how departures from assigned timing were handled, or identify the analysis population. It also does not report missing-data procedures, covariate adjustment, or the statistical methods used to produce the posted comparisons. The original sample-size justification and any multiplicity plan are not reported.

These omissions do not establish that a particular design or analysis problem occurred. They limit what can be independently assessed from the registry record and counsel against extending the primary result to unreported outcomes, participant subgroups, or other settings.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Immediate vs. Delayed Insertion of Copper T 380A IUD After Termination of Pregnancy Over 12-weeks Gestation — NCT00540046.
• Registry record last updated 2015-02-09; status last verified 2015-01.
• Results first posted 2015-01-13.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

21. Record Summary

The registry record describes a completed randomized, parallel-group study sponsored by NYU Langone Health. It compared immediate with delayed insertion of a Copper T 380A IUD after termination of pregnancy over 12 weeks of gestation. The recorded study start is 2007-04 and primary completion is 2010-02; masking is listed as none.

The primary outcome was the number of participants using an IUD 6 months after surgery. The posted counts are 58 in the immediate arm and 25 in the delayed arm, with outcome arm counts of 71 and 88. For delayed versus immediate insertion, the registry reports a risk difference of -0.533, a confidence interval from -0.663 to -0.403, and p < 0.001. Expulsion is listed as a secondary outcome, but no result for it is posted. Important analysis details, including missing-data handling and analysis populations, are not reported in the registry record.